Surface of molded products generally have various indications such as a date of production, lot number, product number and so on by which producers can clear up causes of inferior molded products or check their stock.
A marking device is removably inserted into a mold with its indication portion facing the inner surface of the mold and held there during molding so that the above mentioned indications carried on the indication portion can be marked on each molded product.
Such conventional marking device is disclosed in Japanese Patent No. 3470880. FIG. 6 represents the marking device disclosed in the patent.
As shown in FIG. 6, a conventional marking device (100) is mainly composed of an external tube (101) that is marked with letters on its upper surface and an indicator axle (102) that is rotatably inserted in the external tube (101).
Such conventional marking device (100) is utilized, for example, to mark molded items with manufacturing month and manufacturing year. In this case, as shown in FIG. 6, the upper surface of the external tube (101) is marked with numbers 1–12 that represent the manufacturing month and the indicator axle (102) is marked with a number (the example of FIG. 6 shows numbers “02” standing for the year of 2002) that represents the manufacturing year.
The marking device of this type has one problem when it is used to leave marks with different meanings such as “manufacturing month” and “manufacturing year” on molded items. That is, explaining with the example shown above, indicator axle (102) has to be replaced at the change of the year. This replacement requires a huge amount of work in a case plural molds are used to manufacture molded items.
In Japanese utility model publication No. S63-101519A, another type of marking device is disclosed. FIG. 7 shows the marking device disclosed in the utility model publication. FIG. 7(a) is a plain view of the marking device of the utility model publication. FIG. 7(b) represents a jig for rotatably operating the marking device of FIG. 7(a).
Referring to FIG. 7, the marking device (200) disclosed in the utility model publication has a fixed tube (201) that is fixedly mounted to a molding device, a plurality of rotatable tubes (202) that is rotatably inserted in the fixed tube (201) and an indicator axle (203) that is disposed rotatably around the axis of the fixed tube (201). Each rotatable tube (202) is marked with letters on its upper surface.
This type of the marking device (200) is preferably used to leave marks with different meanings since the device has plurality of rotatable tubes (202).
However in rotating operation of the marking device disclosed in the above mentioned utility model publication, a jig for rotating operation (205) shown in FIG. 7(b) is required. To rotate the rotatable tube (202), it is necessary to insert the tip of a two-forked to a concave portion (221) provided on the upper surface of the rotatable tube (202) and to rotate the jig (205) for rotating operation around the axis. In this operation, the adjacent rotatable tube (202) may rotate with the rotatable tube (202) to be rotated with the jig. Therefore adjustment of the marks on the upper surface of the marking device (200) is cumbersome.
The object of the present invention is, in consideration of the above, to provide a removable marking device for a mold that enables to leave two marks with different meanings accurately with simple operation.
According to the invention described in claim 1, the marking device facilitates the adjustment of the marked letters on the upper surface of the device by using a control mechanism that decides whether the indicator axle alone is allowed to rotate or both the indicator axle and the rotatable tube are allowed to rotate depending on the rotating direction of the indicator axle.
According to the invention described in claim 2 and 3, it is possible to position the rotatable tube in given places so as to improve the accuracy of positioning the marked letters on the upper surface of the marking device.
According to the invention described in claim 4 and 5, constant angular position of the base member with respect to the fixed tube is achieved to prevent the positioning error while assembling the marking device.
According to the invention described in claim 6, it is possible to prevent external substance such as dust from entering the marking device in order to avoid disorder of the control mechanism inside the marking device.
According to the invention described in claim 7, it is possible to adjust the position of the marked letters easily.